System and method for detecting and resolving conflicts

ABSTRACT

A method for operating a first device includes transmitting a conflict query frame including a first address field containing a first locally assigned identifier associated with the first device, wherein the conflict query frame further includes a second address field and has a structure of a first legacy frame, and determining if a conflict notification corresponding to the conflict query frame is received within a specified time interval after transmitting the conflict query frame. The method also includes discontinuing use of the first locally assigned identifier if the conflict notification is received within the specified time interval, and continuing use of the first locally assigned identifier if the conflict notification is not received within the specified time interval.

This application is a continuation of U.S. patent application Ser. No.14/301,232, filed Jun. 10, 2014, now allowed, entitled “System andMethod for Detecting and Resolving Conflicts,” which claims the benefitof U.S. Provisional Application No. 61/839,178, filed on Jun. 25, 2013,entitled “Method and System for Detecting and Resolving a Conflict ofIdentities,” all of which applications are hereby incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates generally to digital communications, andmore particularly to a system and method for detecting and resolvingconflicts.

BACKGROUND

A neighbor awareness networking (NAN) certification program is currentlybeing developed by the Wi-Fi Alliance NAN Technical Task Groups toprovide Wi-Fi technology with a low-power mechanism that is run indevices in the background to make the devices neighbor aware. The NANwill enable mobile devices to efficiently discover people and servicesoperating within their proximity. The NAN should scale effectively indense Wi-Fi environments and complement the high data rate connectivityof Wi-Fi by providing information about people and services in theproximity. It is envisioned that the typical applications for NANinclude Wi-Fi based mobile social networking, mobile commerce, mobileadvertising, wireless multi-player gaming, and the like.

SUMMARY OF THE DISCLOSURE

Example embodiments of the present disclosure which provide a system andmethod for detecting and resolving conflicts.

In accordance with an example embodiment of the present disclosure, amethod for operating a first device is provided. The method transmittinga conflict query frame including a first address field containing afirst locally assigned identifier associated with the first device,wherein the conflict query frame further includes a second address fieldand has a structure of a first legacy frame, and determining if aconflict notification corresponding to the conflict query frame isreceived within a specified time interval after transmitting theconflict query frame. The method also includes discontinuing use of thefirst locally assigned identifier if the conflict notification isreceived within the specified time interval, and continuing use of thefirst locally assigned identifier if the conflict notification is notreceived within the specified time interval.

In accordance with another example embodiment of the present disclosure,a method for operating a second device is provided. The method includesreceiving a conflict query frame including a first address fieldcontaining a first locally assigned identifier associated with a firstdevice, wherein the conflict query frame further includes a secondaddress field and has a structure of a first legacy frame, andtransmitting a conflict response frame, beginning at a specified time,in response to determining that the first locally assigned identifiermatches a second locally assigned identifier associated with the seconddevice, wherein the conflict response frame has a structure of a secondlegacy frame. The conflict response frame includes a third address fieldcontaining a first value that is equal to a second value contained inthe second address field, and a second Duration field including a thirdvalue that is equal to a fourth value included in a first Duration fieldof the conflict query frame minus a sum of a duration of the conflictresponse frame and a duration of a short inter-frame space.

In accordance with another example embodiment of the present disclosure,a method for operating a first IEEE 802.11 compliant device is provided.The method includes transmitting a Request-to-Send frame including afirst Receiver Address field containing a first locally assignedidentifier associated with the first IEEE 802.11 compliant device,wherein the Request-to-Send frame also includes a Transmitter Addressfield, and determining if a Clear-to-Send frame corresponding to theRequest-to-Send frame is received within a specified time interval aftertransmitting the Request-to-Send frame, wherein the Clear-to-Send frameincludes a second Receiver Address field containing a first value thatis equal to a second value contained in the Transmitter Address field.The method also includes discontinuing use of the first locally assignedidentifier if the Clear-to-Send frame corresponding to theRequest-to-Send frame is received within the specified time interval,and continuing use of the first locally assigned identifier if theClear-to-Send frame corresponding to the Request-to-Send frame is notreceived within the specified time interval.

In accordance with another example embodiment of the present disclosure,a method for operating a second IEEE 802.11 compliant device isprovided. The method includes receiving a Request-to-Send frameincluding a first Duration field, a first Receiver Address field, and aTransmitter Address field, and determining if the Request-to-Send frameis for testing potential conflict with a first locally assignedidentifier associated with a first IEEE 802.11 compliant device, whereinthe first locally assigned identifier is contained in the first ReceiverAddress field. The method also includes determining if the first locallyassigned identifier matches a second locally assigned identifierassociated with the second IEEE 802.11 compliant device, in response todetermining that the Request-to-Send frame is for testing potentialconflict, and transmitting a Clear-to-Send frame, beginning at aspecified time, in response to determining that the first locallyassigned identifier matches the second locally assigned identifier. TheClear-to-Send frame includes a second Receiver Address field containinga first value that is equal to a second value contained in theTransmitter Address field, and a second Duration field including a thirdvalue that is equal to a fourth value included in the first Durationfield minus a sum of a duration of the Clear-to-Send frame and aduration of a short inter-frame space.

In accordance with another example embodiment of the present disclosure,a device is provided. The device includes a transmitter, a receiver, anda processor operatively coupled to the transmitter and to the receiver.The transmitter transmits a conflict query frame including a firstaddress field containing a locally assigned identifier associated withthe device, wherein the conflict query frame further includes a secondaddress field and has a structure of a first legacy frame. The receiverreceives frames. The processor determines if a conflict notificationcorresponding to the conflict query frame is received within a specifiedtime interval after transmitting the conflict query frame, discontinuesuse of the locally assigned identifier if the conflict notification isreceived within the specified time interval, and continues use of thelocally assigned identifier if the conflict notification is not receivedwithin the specified time interval.

In accordance with another example embodiment of the present disclosure,a device is provided. The second device includes a receiver, a processoroperatively coupled to the receiver, and a transmitter operativelycoupled to the processor. The receiver receives a conflict query frameincluding a first address field containing a first locally assignedidentifier associated with a first device, wherein the conflict queryframe further includes a second address field and has a structure of afirst legacy frame. The processor determines if the first locallyassigned identifier matches a second locally assigned identifierassociated with the second device. The transmitter transmits a conflictresponse frame, beginning at a specified time, in response todetermining that the first locally assigned identifier matches thesecond locally assigned identifier, wherein the conflict response framehas a structure of a second legacy frame. The conflict response frameincludes a third address field containing a first value that is equal toa second value contained in the second address field, and a secondDuration field including a third value that is equal to a fourth valueincluded in a first Duration field of the conflict query frame minus asum of a duration of the conflict response frame and a duration of ashort inter-frame space.

One advantage of an embodiment is that conflicts, such as in addressesand/or identifiers, may be readily detected and resolved.

A further advantage of an embodiment is that the techniques presentedherein are compatible with legacy devices.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an example communications system according to exampleembodiments described herein;

FIG. 2 illustrates a diagram of example channel access timing accordingto example embodiments described herein;

FIG. 3 illustrates a transmission diagram of example transmissions andstates made by devices utilizing request-to-send (RTS) and clear-to-send(CTS) frames to reserve the wireless channel prior to the actual datatransmission according to example embodiments described herein;

FIG. 4A illustrates an example RTS frame;

FIG. 4B illustrates an example CTS frame;

FIG. 5 illustrates an example MAC address;

FIG. 6 illustrates a flow diagram of example operations occurring in aNAN compliant device as the NAN compliant device tests an identifier forconflict according to example embodiments described herein;

FIG. 7 illustrates a flow diagram of example operations occurring in aNAN compliant device as the NAN compliant device responds to a conflictquery frame according to example embodiments described herein;

FIG. 8 illustrates a flow diagram of example operations occurring in aNAN compliant device as the NAN compliant device responds to a conflictquery frame according to example embodiments described herein;

FIG. 9 illustrates an example first communications device according toexample embodiments described herein; and

FIG. 10 illustrates an example second communications device according toexample embodiments described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The operating of the current example embodiments and the structurethereof are discussed in detail below. It should be appreciated,however, that the present disclosure provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificstructures of the disclosure and ways to operate the disclosure, and donot limit the scope of the disclosure.

One embodiment of the disclosure relates to detecting and resolvingconflicts of identifiers that are assigned to different communicationsstations in a distributed or uncoordinated manner. For example, a firstdevice transmits a conflict query frame including a locally assignedidentifier associated with the first device in a first address field ofthe conflict query frame, discontinues use of the locally assignedidentifier in response to determining that a conflict notificationcorresponding to the conflict query frame is received within a specifiedtime interval after transmitting the conflict query frame, and continuesuse of the locally assigned identifier in response to determining thatthe conflict notification corresponding to the conflict query frame isnot received within the specified time interval.

The present disclosure will be described with respect to exampleembodiments in a specific context, namely IEEE 802.11 compliantcommunications systems that support neighbor awareness networking (NAN)protocols. The disclosure may be applied to standards compliantcommunications systems, such as those that are compliant with ThirdGeneration Partnership Project (3GPP), IEEE 802.11, WiFi Alliance, andthe like, technical standards, and non-standards compliantcommunications systems, that neighbor awareness networking or similarprotocols.

FIG. 1 illustrates an example communications system 100. Communicationssystem 100 includes an access point (AP) 105 that serves one or morestations, such as stations (STA) 110-116, by receiving communicationsoriginating from the stations and then forwarding the communications totheir intended destinations or receiving communications destined to thestations and then forwarding the communications to their intendedstations. In addition to communicating through AP 105, some stations maydirectly communicate with one another. As an illustrative example,station 116 may transmit directly to station 118. APs may also becommonly referred to as NodeBs, evolved NodeBs (eNBs), base stations,controllers, communications controllers, and the like. Stations may alsobe commonly referred to as mobile stations, mobiles, user equipment(UE), terminals, users, subscribers, and the like.

While it is understood that communications systems may employ multipleAPs capable of communicating with a number of stations, only one AP, anda number of stations are illustrated for simplicity.

In Wi-Fi systems, transmissions to and/or from a station occur on ashared wireless channel. Wi-Fi systems make use of carrier sensemultiple access with collision avoidance (CSMA/CA), where a stationdesiring to transmit needs to determine that the wireless channel isidle before it can transmit. The use of CSMA/CA helps to reduce thecollision probability between transmissions from multiple Wi-Fi devices,which are also known as stations (STAs) or simply devices. A station maydetermine the state of the wireless channel using the station'stransmitter status, and both the physical and virtual carrier sense (CS)functions. When either CS function indicates that the wireless channelis busy or when the station is transmitting, the wireless channel isconsidered busy; otherwise, the wireless channel is considered idle. Thephysical CS function is provided by the physical layer using carriersense/clear channel assessment (CS/CCA) procedure, which basicallyinvolves measuring the received radio frequency (RF) energy on aselected channel and comparing it with a CCA threshold. The CS/CCAprocedure returns an indication of either busy or idle on the measuredchannel based on the result of the comparison. The virtual CS functionis provided by the media access control (MAC) layer using a networkallocation vector (NAV). NAV is an indicator, maintained by eachstation, of time periods when transmission onto the wireless channel isnot initiated by the station. A station receiving a valid frame wherethe value in the Address 1 field, which is also known as the ReceiverAddress (RA) field, in the MAC header of the frame is not the MACaddress of the station should update its NAV with the value received inthe Duration field in the MAC header of the frame. The NAV may bethought of as a counter, which counts down to 0 at a uniform rate. Whenthe counter is 0, the virtual CS function indicates that the wirelesschannel is idle; when nonzero, the wireless channel is busy.

FIG. 2 illustrates a diagram 200 of example channel access timing. Afirst trace 205 represents channel access for a first station (STA 1), asecond trace 207 represents channel access for a second station (STA 2),and a third trace 209 represents channel access for a third station (STA3). At the end of a frame, each station wishing to transmit determinesthat the wireless channel is idle through the use of the CS functionsover a time interval referred to as an inter-frame space (IFS).Different IFSs are defined to provide priority levels for access to thewireless channel. A short inter-frame space (SIFS) is the shortest ofthe IFSs between transmissions from different stations. A SIFS isusually used between the RTS frame and corresponding CTS frame, orbetween the data frame and corresponding ACK frame, without using abackoff period. A point coordination function (PCF) inter-frame space(PIFS) is used, usually by an AP, to gain priority access to thewireless channel for transmitting certain types of management frames,without using a backoff period. A distributed coordination function(DCF) inter-frame space (DIFS) may last longer than both the SIFS andthe PIFS. A station desiring to initiate the transmission of a dataframe should invoke the CS functions to determine that the wirelesschannel is idle for a period of DIFS. After the channel is idle for aperiod of DIFS, the station generates a random backoff period foradditional deferral time before transmitting. This random backoffprocess minimizes the chances of collisions during contention betweenmultiple stations that have been deferring to the same event.

However, collisions may still happen, especially when there is a hiddennode in the system. When a collision does happen between large dataframes, a large chunk of air time may be wasted as the collided framesmay not be received correctly and retransmission(s) is made. FIG. 3illustrates a transmission diagram 300 of example transmissions andstates made by devices utilizing request-to-send (RTS) and clear-to-send(CTS) frames to reserve the wireless channel prior to the actual datatransmission. A first trace 305 illustrates transmissions made by asource device, a second trace 310 illustrates transmissions made by adestination device, and a third trace 315 illustrates states of otherdevices. In addition to CSMA/CA, the RTS and/or CTS frames may be usedto reserve the wireless medium for transmission of large frame(s) toavoid excessive loss of air time if a collision happens. A Durationfield in the RTS frame and CTS frame is set to a value that protects upto the end of a wireless medium reservation period which covers theanticipated CTS frame (for RTS frame only), the pending data frametransmission, the anticipated acknowledge (ACK) frame for acknowledgingthe data frame, and the SIFSs required between the frames. A third-partydevice receiving the RTS or CTS frame uses the Duration value to set itsnetwork allocation vector (NAV) to avoid contending for the wirelessmedium during the reserved period. With the RTS/CTS reservationmechanism, even if a collision happens due to the hidden node, the airtime lost is much smaller since the RTS/CTS frames are usually muchsmaller than the data frames.

As shown in FIG. 3, after a DIFS period, the source device may transmitan RTS frame 320. RTS frame 320 may be addressed to the destinationdevice and include a Duration field set to a value that covers to theend of a wireless medium reservation period, including an anticipatedCTS frame, data frame, acknowledgement frame, and associated SIFSperiods. RTS frame 320 may also include a MAC address of the sourcedevice in a transmitter address (TA) field of RTS frame 320. Thedestination device, after receiving RTS frame 320 may respond with a CTSframe 325 after waiting a SIFS period. CTS frame 325 may acknowledgethat the source device is clear to transmit, which it does (a data frame330) after another SIFS period. CTS frame 325 may be addressed to thesource device by including the MAC address of the source device, whichis obtained from the TA field of RTS frame 320, in a receiver address(RA) field of the CTS frame 325. Furthermore, CTS frame 325 may includea Duration field set to a value that covers to the end of a wirelessmedium reservation period by setting the value in the Duration field ofCTS frame 325 to the value in the Duration field of the RTS frame 320minus a sum of a duration of the CTS frame 325 and a duration of a SIFT.After receiving the CTS frame 325 corresponding to the RTS frame 320(meaning the RA in the received CTS frame matches or is equal to the TAin the transmitted RTS frame), the source device may transmit the dataframe 330 to the destination device after yet another SIFS period. Afterreceiving the data frame 330, the destination device may transmit anacknowledgement frame 335 after yet another SIFS period.

The other devices that receive RTS frame 320 may set their NAV inaccordance with a Duration field of RTS frame 320 (shown as NAV 340).Similarly, the other devices that receive CTS frame 325 may set theirNAV in accordance with a Duration field of CTS frame 325 (shown as NAV345). It is noted that although RTS frame 320 and CTS frame 325 may bereceived at different times, due to the different values of the Durationfields, the ends of the wireless medium reservation periods in the NAVoccur at substantially the same time. The devices may contend for accessto the wireless medium after a DIFS period.

FIG. 4a illustrates an example RTS frame 400. RTS frame 400 may includea frame control field 405, a Duration field 410, a receiver address (RA)field 415, a transmitter address (TA) field 420, and a frame checksequence (FCS) field 425. Frame control field 405 may include controlinformation, including a Type field and a Subtype field indicating thatthe frame is an RTS frame. Duration field 410 may specify a duration ofa wireless medium reservation period, starting from the end of the RTSframe. RA field 415, also referred to as the Address 1 field, mayspecify a MAC address of an intended receiving device of RTS frame 400.TA field 415, also referred to as the Address 2 field, may specify a MACaddress of a source device of RTS frame 400. FCS field 425 may include acyclic redundancy check value for RTS frame 400.

FIG. 4b illustrates an example CTS frame 450. CTS frame 450 may includea frame control field 455, a Duration field 460, an RA field 465, and aFCS field 470. Frame control field 455 may include control information,including a Type field and a Subtype field indicating that the frame isa CTS frame. Duration field 460 may specify a duration of a wirelessmedium reservation period, starting from the end of the CTS frame. RAfield 465 may specify a MAC address of an intended receiving device ofCTS frame 450. FCS field 470 may include a cyclic redundancy check valuefor CTS frame 450.

In a NAN compliant communications system, a NAN-capable Wi-Fi device (orNAN device) can be identified by its MAC address. In a Wi-Fi system, aMAC address is a 6-octet long MAC Layer identifier of a device. FIG. 5illustrates an example MAC address 500. As shown in FIG. 5, a leastsignificant bit (LSB) 505 of Octet 0 of 6-octet long MAC Address 500,may be referred to as an Individual/Group (I/G) address bit, indicatesif MAC address 500 is an individual MAC address or a group MAC address.A bit 510 next to the LSB of Octet 0 of 6-octet long MAC Address 500,may be referred to as a Universal/Local (U/L) address bit, indicates ifMAC address 500 is a globally unique MAC address (which may also bereferred to as a hardware MAC address) or a locally assigned MACaddress.

A MAC address may be carried in the RA field, which is also referred toas an Address 1 field, of a MAC header of a frame to identify theintended recipient of the frame. A MAC address may be carried in the TAfield, which is also referred to as an Address 2 field, of the MACheader of a frame to identify the transmitting device of the frame.

Furthermore, in a NAN compliant communications system, a NAN group isidentified by a NAN Cluster ID, which is 6-octect long (same as the MACaddress). It has been proposed that a NAN Cluster ID can only take avalue (with hexadecimal representation) from 50-6F-9A-<TBD>-00-00 to50-6F-9A-<TBD>-FF-FF, thereby only allowing 65536 possible NAN ClusterIDs. The value of Octet 3 of the NAN Cluster ID is to be decided (TBD)by the standard body. The NAN Cluster ID of a NAN group is generallyrandomly chosen from within the allowed range at the start of the NANgroup by the device that initiates the NAN group.

Generally, in a service oriented computing system or communicationssystem, a service that is being advertised or sought may be identifiedby a service name. In Wi-Fi Alliance's (WFA's) Wi-Fi Direct Services(WFDS) specification project, a Service ID (or Service Hash), which is a6-octet-long truncated hash output of the service name, is used toidentify the service in the very first message frame (Probe Requestframe). Then the service name is used in the subsequent message frames.

The NAN protocol places privacy protection high on a list of priorities.The globally unique MAC address of a device, if revealed in a frame thatthe device sends, for example, in the TA field of the frame, may be usedby others to identify the device and/or to track the movement of thedevice, thereby the movement of the user of the device. One of the waysthat privacy is protected is that the MAC address used in the framessent by a NAN compliant device during a pre-association servicediscovery phase may be a local and/or temporary MAC address that the NANcompliant device generates, for example, randomly, and assigns toitself. The NAN compliant device's globally unique (and permanent) MACaddress may be used only when a connection is needed or only after asecurity protection mechanism (such as a shared encryption key) has beenestablished. In such a situation, there is a small (but non-zero) chancethat the local MAC address that the NAN compliant device assigns toitself may conflict with (i.e., happen to be the same as) a MAC addressalready being used by another NAN compliant device or a legacy device.Furthermore, a NAN cluster identifier (a NAN cluster ID) is alsorandomly chosen from within a limited range in a distributed manner byan organizer of a NAN group. Hence, in a high density environment, theNAN cluster identifiers of different NAN groups may also conflict. Sucha conflict of identifiers may cause protocol errors and compromise thesystem robustness.

In a more general case, in any future evolution of 802.11/Wi-Fitechnology, it may become desirable to provide privacy protection byusing a locally generated identifier of a device for identifying thedevice at the MAC layer level, and this locally generated identifier isalways decoupled from the globally unique MAC address or any upper layeridentifier of the device that may reveal the true identity of the deviceor the end user. In those circumstances, especially in high-densityenvironments, a conflict of locally generated identifiers betweendifferent devices may occur and may cause protocol errors. Thus, amechanism to detect and resolve such conflicts is needed.

According to an example embodiment, MAC layer frames may be used todetect a potential conflict of identifier. As an illustrative example, aConflict Query frame and a Conflict Response frame may be used to detecta potential conflict of identifier. As another illustrative example fordetecting a potential conflict of identifier, in an IEEE 802.11 or WFAcompliant communications system, the RTS frame may be reused as theConflict Query frame such that the Conflict Query frame has not only thesame structure of the RTS frame but also the same values in the Type andSubtype fields as those in the RTS frame, and the CTS frame may bereused as the Conflict Response frame such that the Conflict Responseframe has not only the same structure of the CTS frame, but also thesame values in the Type and Subtype fields as those in the CTS frame. Asyet another illustrative example for detecting a potential conflict ofidentifier, in an IEEE 802.11 or WFA compliant communications system,the RTS frame may be reused as the Conflict Query frame such that theConflict Query frame has not only the same structure of the RTS framebut also the same values in the Type and Subtype fields as those in theRTS frame, while the Conflict Response frame has the same structure ofthe CTS frame but has a different value in the Type or Subtype field asthat in the CTS frame to indicate that the Conflict Response frame isdifferent from the CTS frame. The RTS and CTS frames may be used in sucha way that preserves backwards compatibility with legacy devices. Asignificance of reusing the RTS and CTS frames is that a legacy devicecan react to the RTS-like Conflict Query frame and the CTS-like ConflictResponse frame properly based on the legacy rules of behaviors, and moreimportantly, if a conflict with a MAC address of a legacy device exists,reusing the RTS frame as the Conflict Query frame enables the legacydevice to send a response to the Conflict Query frame based on thelegacy rules of behavior and the response will be interpreted as anotification of a conflict, as a Conflict Response frame is, by theinitiating device of the Conflict Query frame.

According to an example embodiment, a NAN compliant device may transmita MAC layer frame used for conflict query, such as a Conflict Queryframe, a RTS frame, and the like, to test the existence of a candidateidentifier, such as a MAC address, a NAN cluster identifier, a serviceidentifier, a group identifier, and the like, before adopting the use ofthe candidate identifier or when the NAN compliant device suspects thatthere has been a conflict with the identifier that it is using. Such aframe may be referred to in general as a conflict query frame. A causeof suspecting a conflict with an identifier being used may be anunusually high rate of protocol errors, higher layer data errors ordecryption failures in spite of a high rate of success in decoding theMAC layer frames. In general, conflicts of identifiers that are assignedin a distributed or un-coordinated manner may be checked using theexample embodiments disclosed herein. As an illustrative example, theconflict query frame may reuse the frame structure of a RTS frame (shownin FIG. 4a ). In the conflict query frame, a frame control field mayfurther be set identical to the one in a conventional RTS frame that issent to reserve the wireless medium for data transmission, meaning thatframe type and subtype fields in the frame control field indicate thatthe conflict query frame is an RTS frame. Identifying the conflict queryframe as an RTS frame is for compatibility reasons and to allow legacydevices to possibly participate in sending a conflict notification.

A Duration field in the conflict query frame may be used to set the NAVof non-responding stations to a value that covers to the end of ananticipated MAC layer frame used for conflict response or ConflictResponse frame, which has the frame structure of a CTS frame (shown inFIG. 4b ), so there is no pending data frame or acknowledgement (ACK)frame. Such a Duration value is a fixed value since the lengths of theConflict Response frame and the SIFS gap are fixed. And such a Durationvalue is generally shorter than a typical Duration value in aconventional RTS frame when a pending data frame and ACK frame normallyfollow. The MAC layer frame used for conflict response or ConflictResponse frame may be referred to as a conflict response frame. Theuntypical value in the Duration field of a conflict query frame may beused by the NAN compliant devices to differentiate the conflict queryframe from a conventional RTS frame. With the frame differentiated(either as the conflict query frame, or the conventional RTS frame), theNAN compliant device may interpret the remaining fields of the frameaccording to the differentiation.

An Address 1 field, which is also known as the receiver address (RA)field, of the conflict query frame may be set to the candidateidentifier, such as the candidate local MAC address, the candidate NANcluster ID, the candidate service identifier, the candidate groupidentifier, and the like, of the NAN compliant device transmitting theconflict query frame instead of the globally unique MAC address of anintended receiving device as in a conventional RTS frame. An Address 2field, which is also known as the transmitter address (TA) field, of theconflict query frame may be set to the candidate identifier of the NANcompliant device transmitting the conflict query frame as well. As anillustrative example, consider a situation wherein candidate local MACaddresses are being tested for conflict. Since the NAN compliant doesnot yet have a MAC address (a non-permanent local MAC address), it isnatural to use the candidate local MAC address as the transmitteraddress in the Address 2 field. It is noted that setting the Address 1field and the Address 2 field to the same value may be used tofacilitate another technique to differentiate the conflict query framefrom a conventional RTS frame, or to eliminate possible erroneousframes.

According to an example embodiment, when a NAN compliant device receivesthe conflict query frame testing a candidate identifier that matcheswith a local identifier of the NAN compliant device, the NAN compliantdevice may send back a conflict response frame, and the like, to notifyof or indicate the existence of a conflict with the candidateidentifier. As an illustrative example, the conflict response frame mayreuse the frame structure of a CTS frame (shown in FIG. 4b ). In theconflict response frame, a frame control field may further be set to beidentical to the one in a conventional CTS frame, meaning that frametype and subtype fields in the frame control field indicate that theconflict response frame is a CTS frame. Identifying the conflictresponse frame as a CTS frame is for compatibility reasons.

As in the RTS and CTS frames, a Duration field in the conflict responseframe may be set to the value obtained from the Duration field of thecorresponding conflict query frame subtracted by the sum of durations ofthe conflict response frame and of a SIFT, so that values in bothDurations fields cover to the same end of the wireless mediumreservation period. As a result, if the Duration field in thecorresponding conflict query frame is set to a value that equals to thesum of durations of the conflict response frame and of a SIFT, theDuration field in the conflict response frame is set to zero, meaningthat the wireless medium will be free at the end of the conflictresponse frame (for no data frame nor ACK frame follows). Such anuntypical value in the Duration field of the conflict response frame maybe used to differentiate the conflict response frame from a conventionalCTS frame that is normally followed by a data frame and ACK frame. AnAddress 1 field of the conflict response frame may be set to the samevalue as the Address 2 field in the corresponding conflict query frame.This is also consistent with technical standards requirements that theAddress 1 field in a first frame sent in response to a second frame isthe same as the Address 2 field of the second frame.

A legacy device that receives an RTS-frame-based conflict query framemay determine that it is a RTS frame, since the Type and Subtype fieldsin the frame control field of the conflict query frame indicate so. If aMAC address of the legacy device matches with the value in the Address 1field of the RTS-frame-based conflict query frame (which carries thecandidate identifier being tested), the legacy device may send back aCTS frame with the Duration field set to the value of the Duration fieldof the received conflict query frame subtracted by the sum of durationsof a CTS frame and of a short inter-frame space. This is based on thelegacy rules of behavior when sending a CTS frame in response toreceiving an RTS frame. This legacy behavior ensures that the Durationfield in the CTS frame has a consistent end of wireless mediumprotection coverage as that of the Duration field of the frame causingthe CTS frame. Because the Duration field in the received conflict queryframe has a value that equals to the sum of durations of a conflictresponse frame, which has the same duration as a CTS frame for havingthe same structure of, and of a short inter-frame space, the subtractioncauses the Duration field in the CTS frame sent to be zero (i.e., thewireless medium becomes free at the end of the CTS frame). The CTS framesent by the legacy device also includes the RA field with value set tothe content of the Address 2 field of the seemingly RTS frame (butactually a conflict query frame) received by the legacy device. This isalso based on the legacy rules of behavior when sending a CTS frame inresponse to receiving a RTS frame. If the MAC address of the legacydevice does not match with the value in the Address 1 field of theconflict query frame, the legacy device may set its NAV according to thevalue of the Duration field of the conflict query frame, which is up tothe end of the conflict response frame. Therefore, the legacy device mayreturn to contending for the communications medium after the conflictresponse frame and loses no time.

In general, when a first NAN compliant device that is an originator ofthe conflict query frame, receives either a conflict response frame froma second NAN compliant device or a CTS frame from a legacy device, thefirst NAN compliant device may deem that there is a conflict with thecandidate identifier included in the conflict query frame. On the otherhand, receiving no conflict response frame or CTS frame within apre-defined responding time may be an indication that there is noconflict. As a result of detecting a conflict, the first NAN compliantdevice may decide to try another candidate identifier in an attempt toresolve the identifier conflict. To do so, the first NAN compliantdevice may select a new candidate identifier and send a new conflictquery frame with the new candidate identifier stored in the Address 1and Address 2 fields. If the first NAN compliant device receives noconflict response frame or CTS frame corresponding to the new conflictquery frame, the first NAN compliant device may deem that there is noconflict related to the new candidate identifier and may commence usingthe new candidate identifier. It is noted that response timing of theconflict response frame to the conflict query frame is substantially thesame as that of a conventional CTS frame to a conventional RTS frame,which is fixed and short, thereby helping the first NAN compliant deviceto quickly determine if there is a conflict with the candidateidentifier(s).

In a situation where MAC layer frames used for conflict query andconflict response are used to detect multiple identifier conflicts, anidentifier type field may be used to indicate which type of identifieris being checked. However, if the frame format of legacy frames, such asRTS and CTS frames, are used for the conflict query and conflictresponse, there may a lack of space to add an identifier type field dueto a need for backwards compatibility with the legacy RTS and CTSframes.

According to an example embodiment, if a NAN compliant device uses afirst identifier, such as a locally assigned MAC address as its NANInterface Address, the next-to-LSB of Octet 0 (i.e., the U/L address bit510 of FIG. 5) of the 6-octet long MAC address must be “1”. Since aglobally assigned MAC address is always unique and never needs to bechecked for conflict, if a conflict query frame is sent to test acandidate MAC address, it must be a local MAC address; therefore thenext-to-LSB of Octet 0 (i.e., the U/L address bit 510) of the 6-octetvalue in Address 1 field is “1” if the candidate MAC address is beingconveyed and tested.

It has been proposed to allocate the following range of basic serviceset identifiers (BSSID) (in hexadecimal form) for NAN cluster IDs:50-6F-9A-<TBD>-00-00 to 50-6F-9A-<TBD>-FF-FF. Even though Octet 3 hasnot been determined yet, it is known that Octet 0 will always be “50” inhexadecimal notation, which is “00001010” in binary form, beginning withthe LSB. This means that the next-to-LSB of Octet 0 of any NAN clusterID must be “0”, which is the opposite value of locally generated MACaddresses. This is consistent with the rule that WFA-specificOrganizationally Unique Identifier (OUI) values (the first three octetsof the NAN cluster IDs (i.e., “50-6F-9A”)) are meant to be globallyunique. Hence, the next-to-LSB of Octet 0 of the 6-octet value in theAddress 1 field is “0” if the NAN cluster ID is being conveyed andtested.

Therefore, the next-to-LSB (i.e., the U/L address bit 510 of FIG. 5) ofOctet 0 of the 6-octet value in the Address 1 field may be used as anindication if a local MAC address or NAN cluster ID is being tested. ANAN compliant device that is managing a NAN group, such as a NAN AnchorMaster or a NAN Master, may use both its local MAC address and the NANcluster ID of its NAN group to compare with the value in the Address 1field of a conflict query frame. A NAN compliant device that is notmanaging a NAN group may not respond to a conflict query frame that istesting a NAN cluster ID to avoid too many NAN compliant devicesresponding to the same conflict query frame. Hence, NAN compliantdevices not managing NAN groups may use their local MAC address tocompare with the value in the Address 1 field of a conflict query framewithout determining if the received frame is testing a local MAC addressor a NAN cluster ID, since its own local MAC address will not match witha NAN cluster ID.

According to another example embodiment, the LSB (i.e., the I/G addressbit 505 of FIG. 5) of Octet 0 of the 6-octet value in the RA field maybe used to indicate if a candidate identifier is a local MAC addressthat is normally assigned to an individual device or a group identifierthat will be assigned to a group of devices, as a group identifiershould have the I/G address bit set to “1” while a local MAC addressthat is assigned to an individual device should have the I/G address bitset to “0”.

FIG. 6 illustrates a flow diagram of example operations 600 occurring ina NAN compliant device as the NAN compliant device tests an identifierfor conflict. Operations 600 may be indicative of operations occurringin a NAN compliant device, such as eNB 105 or stations 110-118, as theNAN compliant tests an identifier for conflict.

Operations 600 may begin with the NAN compliant device performing acheck to determine if it needs a new identifier, such as a local MACaddress, NAN cluster ID, and the like (block 605). As an illustrativeexample, the NAN compliant device that is highly sensitive to a user'sprivacy may need a new local MAC address on occasion in order to avoidbeing tracked. As another illustrative example, the NAN compliant deviceinitiating a NAN group may need a NAN Cluster ID. If the NAN compliantdevice determines that it needs a new identifier, the NAN compliantdevice may send a conflict query frame, such as a MAC frame used forconflict query, a Conflict Query frame, a repurposed RTS frame, and thelike (block 610). The conflict query frame may include the identifierinserted in both the Address 1 and Address 2 fields, and a Durationfield set to a value equal to the sum of the lengths, in time, of aConflict Response frame and of a short inter-frame space (SIFS).

If the NAN compliant device determines that it does not need a newidentifier, the NAN compliant device may perform a check to determine ifit suspects a conflict of identifiers, such as a conflicting local MACaddress, a conflicting NAN cluster ID, and the like (block 615). As anillustrative example, the NAN compliant device may receive data framesintended for it (i.e., the MAC address of the NAN compliant devicematches the RA field of the received data frames) but it is unable todecrypt or otherwise parse the data frames of some or all of thereceived data frames. Such a situation may lead the NAN compliant deviceto suspect that there is another device with the same MAC address. Ifthe NAN compliant device suspects that there is a conflict ofidentifiers, the NAN compliant device may send a conflict query frame(block 610) to confirm that.

The NAN compliant device may perform a check to determine if it hasreceived a conflict response frame with a receiver address (i.e. theAddress 1 field) matches with the candidate identifier that the NANcompliant device is testing, such as a MAC frame used for conflictresponse, a Conflict Response frame, a repurposed CTS frame, and thelike, in a timely fashion (block 620). As an illustrative example, theNAN compliant device may expect to receive a conflict response framewithin a small amount of time after a SIFS period. If the NAN compliantdevice does receive a conflict response frame matching to the conflictquery frame in a timely manner, the NAN compliant device may select anew identifier, such as a new MAC address, a new NAN cluster ID, and thelike (block 625). The NAN compliant device may return to block 610 totest the new identifier. If the NAN compliant device does not receive aconflict response frame matching to the conflict query frame in a timelymanner, the NAN compliant device may deem that there is no conflict anduse the identifier (block 630). Operations 600 may terminate. Similarly,if the NAN compliant device does not suspect a conflict of identifiersin block 615, the NAN compliant device may use the identifier (block630).

According to an example embodiment, instead of routinely checking for apotential conflict with some identifiers, the NAN compliant device mayuse the identifier until it suspects that there is a conflict. Since theprobability of an identifier conflict is relatively low (for someidentifiers, such as MAC address) and using communications mediumresources to continually check for potential conflicts, by transmittingconflict query frames, may end up wasting a lot of resources, the NANcompliant device may save significant communications resources if ituses the identifiers and perform a check for conflicts only if itsuspects that there is a conflict. If the NAN compliant device suspectsthat there is a conflict, the NAN compliant device may use a conflictchecking technique, such as the example embodiment disclosed in FIG. 6,to check the identifier for conflict.

According to an example embodiment, for identifiers that have relativelyhigh probability of conflict (such as NAN cluster IDs), especially inhigh density environments, NAN compliant devices using the identifierswith high probability of conflict may use a conflict checking technique,such as the example embodiment disclosed in FIG. 6, to check theidentifier for conflict prior to using the identifier. As anillustrative example, if the identifier is used as a NAN cluster ID, theNAN compliant device may use the example embodiment disclosed in FIG. 6,for example, to test a NAN cluster ID prior to using it to initiate aNAN group. It is noted that it is still possible for a conflict of NANcluster IDs to occur even if the NAN cluster IDs are tested prior touse. In a situation when two independently initiated NAN groups with thesame NAN cluster ID are remotely located and successfully initiatedwithout conflict. When the two NAN groups subsequently moved close toone another, conflicts may arise. When a NAN compliant device(s) that ismanaging the NAN group(s) suspects a conflict, the NAN compliantdevice(s) may use the example embodiment disclosed in FIG. 6 to resolvethe conflict.

FIG. 7 illustrates a flow diagram of example operations 700 occurring ina NAN compliant device as the NAN compliant device responds to aconflict query frame. Operations 700 may be indicative of operationsoccurring in a NAN compliant device, such as eNB 105 or stations110-118, as the NAN compliant device responds to a conflict query frame.

Operations 700 may begin with the NAN compliant device performing acheck to determine if it has received a conflict query frame (block705). The conflict query frame may be received from another NANcompliant device testing an identifier, such as a MAC address, a NANcluster ID, and the like, for a conflict. If the NAN compliant devicedid not receive a conflict query frame, operations 700 may terminate. Ifthe NAN compliant device received a conflict query frame, the NANcompliant device may also perform a check to determine if it is using alocal identifier (block 710). In general, if the NAN compliant device isnot using local identifiers, conflicts may not occur. As an illustrativeexample, if the identifier is a MAC address, then if local MAC addressesare not being used, then conflicts may not exist since global MACaddresses are unique by definition. If the NAN compliant device is notusing local identifiers, operations 700 may terminate.

If the NAN compliant device is using local identifiers, the NANcompliant device may perform a check to determine if the localidentifier matches with a value in an Address 1 field of the conflictquery frame (block 715). If the local identifier does not match with thevalue in the Address 1 field, then there is not a conflict andoperations 700 may terminate. It is noted that the NAN compliant devicemay compare the value in the Address 1 field against more than one localidentifier to determine if there is a match. If there is a match, theNAN compliant device may send a conflict response frame with the localidentifier stored in as a value in a RA field of the conflict responseframe and with a Duration field set to zero (block 720). Operations 700may terminate.

FIG. 8 illustrates a flow diagram of example operations 800 occurring ina NAN compliant device as the NAN compliant device responds to aconflict query frame, wherein the NAN compliant device is utilizing morethan one local identifier. Operations 800 may be indicative ofoperations occurring in a NAN compliant device, such as eNB 105 orstations 110-118, as the NAN compliant responds to a conflict queryframe, wherein the NAN compliant device is utilizing more than one localidentifier.

Operations 800 may begin with the NAN compliant device performing acheck to determine if it has received a conflict query frame (block805). The conflict query frame may be received from another NANcompliant device testing an identifier, such as a MAC address, a NANcluster ID, and the like, for a conflict. If the NAN compliant devicedid not receive a conflict query frame, operations 800 may terminate.The NAN compliant device may also perform a check to determine if it isusing a local MAC address (block 810). If the NAN compliant device isusing a local MAC address, the NAN compliant device may perform a checkto determine if its local MAC address matches a value stored in anAddress 1 field of the conflict query frame (block 815). If there is amatch, the NAN compliant device may send a conflict response frame withthe local MAC address stored in as a value in a RA field of the conflictresponse frame and with a Duration field set to zero (block 820).Operations 800 may terminate.

If there is not a match between the local MAC address and the valuestored in the Address 1 field, or if the NAN compliant device is notusing local MAC addresses, the NAN compliant device may perform a checkto determine if it is managing a NAN group (block 825). If the NANcompliant device is not managing a NAN group, operations 800 mayterminate. If the NAN compliant device is managing a NAN group, the NANcompliant device may perform a check to determine if a NAN cluster ID ofa NAN group managed by the NAN compliant device matches with the valuein the Address 1 field of the conflict query frame (block 830). If thereis no match, operations 800 may terminate. If there is a match, the NANcompliant device may send a conflict response frame with the NAN clusterID stored in as a value in a RA field of the conflict response frame andwith a Duration field set to zero (block 820). Operations 800 mayterminate.

It is noted that although the discussion of operations 800 focuses onlocal MAC addresses and NAN cluster IDs, operations 800 may be used tocheck other identifiers for conflicts. Therefore, the discussion oflocal MAC addresses and NAN cluster IDs should not be construed as beinglimiting to either the scope or the spirit of the example embodiments.

Example embodiments presented herein involve not only detecting andresolving conflicts of addresses or identifiers, but also doing so byreusing existing protocols and frame structures in a backward compatibleway such that a communications system utilizing such embodiments cancoexist with legacy communications systems and devices. In such asituation, in addition to WFA's NAN standards project, it is alsopossible to apply the concepts presented herein to other IEEE 802.11based standards, such as the on-going IEEE 802.11aq Pre-AssociationDiscovery project, WFA's Wi-Fi Direct Service (WFDS) project, WFA'sService Discovery project, and the like, since legacy RTS and CTS framesmay be reused in such systems for detecting potential conflicts of MACaddresses and/or similar identifiers. A benefit of reusing legacy RTSand CTS frames as the Conflict Query and Conflict Response frames,respectively, is that they allow a legacy device to participate indetecting a conflict between its MAC address and the identifier beingtested, and notifying the initiating device of such a conflict using thelegacy frame and legacy rules of behaviors that it is made with. Nohardware or software upgrade is required at the legacy device to do so.Actually, the legacy device is unaware of the new purpose of theseemingly RTS frame received. Comparatively, defining a new ConflictQuery frame and Conflict Response frame with a frame type or subtypevalue that legacy devices don't understand would prevent them fromparticipating in detecting and notifying of the conflict. In that case,although conflicts between NAN compliant devices can be detected andresolved, conflicts between a NAN complaint device and a legacy devicemay still exist and remain undetected. Therefore, in the case where itis desirable to detect a conflict with an identifier of legacy devices,reusing the legacy RTS and CTS frames as the Conflict Query and ConflictResponse frames is preferred.

Additionally, the example embodiments presented herein may be used inany ad-hoc based communications system, to detect and resolve a Layer 2address conflict without requiring the help of Layer 3 addresses, anddoing so by reusing some existing Layer 2 message frames in a backwardcompatible manner so that an enhanced communications system can coexistwith legacy communications systems and devices. Examples of such ad-hocbased communications systems include those based on IEEE 802.15,Bluetooth, ZigBee, and the like.

FIG. 9 illustrates an example first communications device 900.Communications device 900 may be an implementation of a NAN complianttransmitting device, such as a communications controller, such as aneNB, a base station, a NodeB, a controller, and the like, or a UE, suchas a user, a subscriber, a terminal, a mobile, a mobile station, and thelike. Communications device 900 may be used to implement various ones ofthe embodiments discussed herein. As shown in FIG. 9, a transmitter 905is configured to transmit frames, conflict query frames, and the like.Communications device 900 also includes a receiver 910 that isconfigured to receive frames, conflict response frames, and the like.

A query frame processing unit 920 is configured to generate a conflictquery frame, such as a Conflict Query frame, a RTS frame, and the like.Query frame processing unit 920 is configured to insert an identifier tobe tested in both an Address 1 field and an Address 2 field of theconflict query frame. A response frame processing unit 922 is configuredto process a received conflict response frame, such as a ConflictResponse frame, a CTS frame, and the like. Response frame processingunit 922 is configured to determine that an identifier to be tested doesconflict with an identifier at another NAN compliant device or legacydevice. An identifier generating unit 924 is configured to generate anidentifier. Identifier selecting unit 924 is configured to generate anidentifier, such as a MAC address, a NAN cluster ID, and the like, inaccordance with rules associated with the identifier. A conflictidentifying unit 926 is configured to detect a conflict arising from anon-unique identifier. A memory 930 is configured to store identifiers,identifiers to be tested, conflicting identifiers, non-conflictingidentifiers, conflict query frames, conflict response frames, and thelike.

The elements of communications device 900 may be implemented as specifichardware logic blocks. In an alternative, the elements of communicationsdevice 900 may be implemented as software executing in a processor,controller, application specific integrated circuit, or so on. In yetanother alternative, the elements of communications device 900 may beimplemented as a combination of software and/or hardware.

As an example, receiver 910 and transmitter 905 may be implemented as aspecific hardware block, while query frame processing unit 920, responseframe processing unit 922, identifier selecting unit 924, and conflictidentifying unit 926 may be software modules executing in amicroprocessor (such as processor 915) or a custom circuit or a customcompiled logic array of a field programmable logic array. Query frameprocessing unit 920, response frame processing unit 922, identifierselecting unit 924, and conflict identifying unit 926 may be modulesstored in memory 930.

FIG. 10 illustrates an example second communications device 1000.Communications device 1000 may be an implementation of a NAN compliantreceiving device, such as a communications controller, such as an eNB, abase station, a NodeB, a controller, and the like, or a UE, such as auser, a subscriber, a terminal, a mobile, a mobile station, and thelike. Communications device 1000 may be used to implement various onesof the embodiments discussed herein. As shown in FIG. 10, a transmitter1005 is configured to transmit frames, conflict response frames, and thelike. Communications device 1000 also includes a receiver 1010 that isconfigured to receive frames, conflict query frames, and the like.

A query frame processing unit 1020 is configured to process a received aconflict query frame, such as a Conflict Query frame, a RTS frame, andthe like. Query frame processing unit 1020 is configured to determine anidentifier to be tested in the conflict query frame. An identifierprocessing unit 1022 is configured to determine if an identifier storedin an Address 1 field of the conflict query frame conflicts with anidentifier used by communications device 1000. A response frameprocessing unit 1022 is configured to generate a conflict responseframe, such as a Conflict Response frame, a CTS frame, and the like.Response frame processing unit 1022 is configured to generate theconflict response frame if the identifier to be tested as provided inthe received conflict query frame matches with an identifier used bycommunications device 1000. A memory 1030 is configured to storeidentifiers, identifiers to be tested, conflicting identifiers,non-conflicting identifiers, conflict query frames, conflict responseframes, and the like.

The elements of communications device 1000 may be implemented asspecific hardware logic blocks. In an alternative, the elements ofcommunications device 1000 may be implemented as software executing in aprocessor, controller, application specific integrated circuit, or soon. In yet another alternative, the elements of communications device1000 may be implemented as a combination of software and/or hardware.

As an example, receiver 1010 and transmitter 1005 may be implemented asa specific hardware block, while query frame processing unit 1020,identifier processing unit 1022, and response frame processing unit 1024may be software modules executing in a microprocessor (such as processor1015) or a custom circuit or a custom compiled logic array of a fieldprogrammable logic array. Query frame processing unit 1020, identifierprocessing unit 1022, and response frame processing unit 1024 may bemodules stored in memory 1030.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims.

What is claimed is:
 1. A device for detecting and resolving conflicts,the device comprising: a transmitter configured to transmit aRequest-to-Send frame including a Transmitter Address field and a firstReceiver Address field, wherein the first Receiver Address fieldcontains a first locally assigned identifier associated with the device;and a processor operatively coupled to the transmitter, the processorconfigured to determine if a Clear-to-Send is received within aspecified time interval after transmitting the Request-to-Send frame,wherein the Clear-to-Send frame includes a second Receiver Address fieldcontaining a first value equal to a second value contained in theTransmitter Address field, and determine whether to continue use of thefirst locally assigned identifier.
 2. The device of claim 1, wherein thefirst locally assigned identifier comprises one of a local media accesscontrol (MAC) address, a neighbor awareness networking (NAN) clusteridentifier, a service identifier, or a group identifier.
 3. The deviceof claim 1, wherein the Request-to-Send frame further includes a firstDuration field, and wherein the Clear-to-Send frame further includes asecond Duration field having a third value equal to a value of the firstDuration field minus a sum of a duration of the Clear-to-Send frame anda duration of a short inter-frame space.
 4. The device of claim 1,wherein the Clear-to-Send frame is received from a legacy IEEE 802.11compliant device and the first locally assigned identifier contained inthe first Receiver Address field matches a media access control (MAC)address associated with the legacy IEEE 802.11 compliant device.
 5. Thedevice of claim 1, wherein the Clear-to-Send frame is received fromanother device and the first locally assigned identifier contained inthe first Receiver Address field matches a second locally assignedidentifier associated with the other device.
 6. The device of claim 1,wherein the Request-to-Send frame further includes a first Durationfield including a fourth value equal to a sum of a duration of theClear-to-Send frame and a duration of a short inter-frame space.
 7. Thedevice of claim 1, wherein the specified time interval spans ends of theRequest-to-Send frame and the Clear-to-Send frame, and wherein thespecified time interval has a nominal value equal to a sum of a durationof the Clear-to-Send frame and a duration of a short inter-frame space.8. The device of claim 1, wherein the Transmitter Address field includesthe first locally assigned identifier.
 9. The device of claim 1, whereinthe processor configured to determine whether to continue use of thefirst locally assigned identifier comprises: the processor configure todiscontinue use of the first locally assigned identifier if theClear-to-Send frame is received within the specified time interval. 10.The device of claim 1, wherein the processor configured to determinewhether to continue use of the first locally assigned identifiercomprises: the processor configured to continue use of the first locallyassigned identifier if the Clear-to-Send frame is not received withinthe specified time interval.
 11. A device for detecting and resolvingconflicts, the device comprising: a receiver configured to receive aRequest-to-Send frame including a first Duration field, a first ReceiverAddress field, and a Transmitter Address field, wherein the firstReceiver Address field contains a first locally assigned identifierassociated with another device; a processor operatively coupled to thereceiver, the processor configured to determine if the Request-to-Sendframe is for testing potential conflict with the first locally assignedidentifier, and determine if the first locally assigned identifiermatches a second locally assigned identifier associated with the device,in response to determining that the Request-to-Send frame is for testingpotential conflict; and a transmitter operatively coupled to theprocessor, the transmitter configured to transmit a Clear-to-Send frame,beginning at a specified time, in response to determining that the firstlocally assigned identifier matches the second locally assignedidentifier.
 12. The device of claim 11, wherein the Clear-to-Send frameincludes a second Receiver Address field and a second Duration field,the second Receiver Address field containing a first value equal to asecond value contained in the Transmitter Address field, and the secondDuration field including a third value equal to a value included in thefirst Duration field minus a sum of a duration of the Clear-to-Sendframe and a duration of a short inter-frame space.
 13. The device ofclaim 11, wherein the first and the second locally assigned identifierscomprise one of a local media access control (MAC) address, a neighborawareness networking (NAN) cluster identifier, a service identifier, ora group identifier.
 14. The device of claim 11, wherein the processorconfigured to determine if the Request-to-Send frame is for testingpotential conflict comprises: the processor configured to determine ifvalues contained in the first Receiver Address field and the TransmitterAddress field are equal, wherein the Request-to-Send frame is fortesting potential conflict if the values in the first Receiver Addressfield and the Transmitter Address field are equal.
 15. The device ofclaim 11, wherein the processor configured to determine if theRequest-to-Send frame is for testing potential conflict comprises: theprocessor configured to determine if values contained in the firstReceiver Address field and the Transmitter Address field are equal,wherein the Request-to-Send frame is not for testing potential conflictif the values in the first Receiver Address field and the TransmitterAddress field are not equal.
 16. The device of claim 11, wherein theprocessor configured to determine if the Request-to-Send frame is fortesting potential conflict comprises: the processor configured todetermine if the first Duration field contains a fourth value equal to asum of the duration of the Clear-to-Send frame and the duration of theshort inter-frame space, wherein the Request-to-Send frame is fortesting potential conflict if the fourth value is equal to the sum ofthe duration of the Clear-to-Send frame and the duration of the shortinter-frame space.
 17. The device of claim 11, wherein the processorconfigured to determine if the Request-to-Send frame is for testingpotential conflict comprises: the processor configured to determine ifthe first Duration field contains a fourth value equal to a sum of theduration of the Clear-to-Send frame and the duration of the shortinter-frame space, wherein the Request-to-Send frame is not for testingpotential conflict if the fourth value is not equal to the sum of theduration of the Clear-to-Send frame and the duration of the shortinter-frame space.
 18. The device of claim 11, wherein the specifiedtime has a nominal value of a sum of a time when an end of theRequest-to-Send frame is received and the duration of the shortinter-frame space.
 19. A method for detecting and resolving conflicts,the method comprising: receiving a Request-to-Send frame including afirst Duration field, a first Receiver Address field, and a TransmitterAddress field, wherein the first Receiver Address field contains a firstlocally assigned identifier associated with another device; determiningif the Request-to-Send frame is for testing potential conflict with thefirst locally assigned identifier; determining if the first locallyassigned identifier matches a second locally assigned identifierassociated with the device, in response to determining that theRequest-to-Send frame is for testing potential conflict; andtransmitting a Clear-to-Send frame, beginning at a specified time, inresponse to determining that the first locally assigned identifiermatches the second locally assigned identifier.
 20. The method of claim19, wherein the Clear-to-Send frame includes a second Receiver Addressfield and a second Duration filed, the second Receiver Address fieldcontaining a first value equal to a second value contained in theTransmitter Address field, the second Duration field including a thirdvalue equal to a value included in the first Duration field minus a sumof a duration of the Clear-to-Send frame and a duration of a shortinter-frame space.
 21. The method of claim 19, wherein the step ofdetermining if the Request-to-Send frame is for testing potentialconflict comprises: determining if values contained in the firstReceiver Address field and the Transmitter Address field are equal,wherein the Request-to-Send frame is for testing potential conflict ifthe values in the first Receiver Address field and the TransmitterAddress field are equal.
 22. The method of claim 19, wherein the step ofdetermining if the Request-to-Send frame is for testing potentialconflict comprises: determining if the first Duration field contains afourth value equal to a sum of the duration of the Clear-to-Send frameand the duration of the short inter-frame space, wherein theRequest-to-Send frame is not for testing potential conflict if thefourth value is not equal to the sum of the duration of theClear-to-Send frame and the duration of the short inter-frame space. 23.The method of claim 19, wherein the specified time has a nominal valueof a sum of a time when an end of the Request-to-Send frame is receivedand the duration of the short inter-frame space.